1. Field of the Invention
The present invention relates to a semiconductor device.
2. Description of the Related Art
Conventionally, a semiconductor device is known in which a plurality of semiconductor chips are stacked on a substrate, and the semiconductor chips are connected with wirings formed in the substrate through bonding wires, respectively. Further, it is also known that electrical characteristics may be improved in such a semiconductor device by fixing a back surface of each semiconductor chip at predetermined potential such as ground potential, power supply potential or the like by applying a voltage to the back surface of the semiconductor chip.
In order to fix the back surface of the semiconductor chip at the predetermined potential in such a semiconductor device, for example, a relay substrate on which a conductive film is formed is provided between the adjacent semiconductor chips. At this time, the conductive film formed on the relay substrate and the wiring formed in the substrate are connected with each other through a bonding wire so that the predetermined voltage can be applied to the conductive film formed in the relay substrate from the wiring formed in the substrate. Then, the conductive film formed on the relay substrate and the back surface of the semiconductor chip are bonded through a conductive adhesive agent so that the back surface of the semiconductor chip can be fixed at the predetermined potential (see Patent Document 1, for example).
However, in such a semiconductor device, there is a problem in that electrical loss is large because the conductive adhesive agent is used to bond the back surface of the semiconductor chip to the conductive film formed on the relay substrate for fixing the back surface of the semiconductor chip at the predetermined potential.
Further, as the conductive adhesive agent includes conductive filler, there is a problem in that the adhesion becomes weaker compared with a non-conductive adhesive agent (insulating adhesive agent).